Hydraulically pressurized molding apparatus

ABSTRACT

Pressure molding apparatus wherein the movable platen is actuated by a two part piston. The piston parts are separated to form an enclosed space therebetween in the cylinder in which hydraulic fluid is maintained. The fluid advances and retracts with the piston parts and, when pressurized, exerts holding pressure to oppose the molding pressure. The trailing part of the piston is mechanically locked in advanced position during the molding step.

United States Patent [1 1 Valyi [451 Oct. 30, 1973 [54] HYDRAULICALLY PRESSURIZED 2,805,447 9/1957 Voges 425/406 X OL APPARATUS 3,418,692 12/1968 Valyi 425/408 [76] Inventor: Emery I Valyi'i,5200 Sycamore Primary Examiner Robert L. Spice JL 3. y R'Verddle I047] Att0rneyNathaniel L. Leek [22] Filed: June 23, 1972 2] A l 4 [57] ABSTRACT 1 pp 83 Pressure molding apparatus wherein the movable platen is actuated by a two part piston. The piston [52] (1.8. CI 425/408, 425/406, 425/DlG. 220, parts are separated to form an enclosed space thercbe- 100/219 tween in the cylinder in which hydraulic fluid is main- [5 1] Int. Cl. B29c 3/00 tained. The fluid advances and retracts with the piston [58] Field of Search 425/408, 406, 233, parts and, when pressurized; exerts holding pressure to 425/DIG. 220; 100/219 oppose the molding pressure. The trailing part of the piston is mechanically locked in advanced position [56] References Cited during the molding step.

17 Claims, 7 Drawing Figures I-IYDRAULICALLY PRESSURIZED MOLDING APPARATUS This invention relates to molding apparatus and more particularly to apparatus of the type wherein amovable mold part is advanced and retracted over a long stroke in each cycle ofoperation.

An object is to provide apparatus of 'the above type having novel and improved features of operation.

A more specific object is to provide'such an apparatus which is readily adaptable for use withdifferent heights of mold members.

A further object is to provide hydraulically operated apparatus of the above type which is adapted for relatively fast operation and in which the quantity of fluid to be moved at each operation is reduced to a minimum.

A further object is to provide hydraulically operated apparatus of the above type which is adapted to exert high molding pressures and in which the movable platen is moved over a relatively long stroke while requiring the displacement of only relatively small quantities of hydraulic fluid.

Various other objects and advantages will be apparent as the nature of the invention is more fully disclosed.

Molding apparatus of the above type having a platen which is advanced and retracted over a relatively long stroke can be actuated mechanically at a rapid rate, but when so actuated adjustment of the stroke for molds of different sizes is difficult and time consuming. When actuated hydraulically such adjustment is relatively simple but a large cylinder is required in order to produce a high molding pressure, for example, a pressure of many tons. When such a cylinder is made long to produce a long stroke a very large volume of hydraulic fluid must be moved. This requires either a reduction in the speed of operation or the use of a hydraulic system of unacceptable size. i

A specific object of the present invention is to provide a hydraulically operated system which is capable of rapid operation over a long stroke without the pumping of excessive quantities of hydraulic fluid. At the same time the hydraulic system provides simple and efficient means for adjusting the stroke to dies of different sizes as required in normal commerical operation.

' The nature of the invention will be better understood from the following description, taken in connection with the accompanying drawings in which certain specific embodiments have been set forth for purposes of illustration.

In the drawings:

FIG. 1 is an elevation of a molding apparatus embodying the invention;

FIG. 2 is a section taken on-the line 2-2 of FIG. 1 but on a larger scale showing the construction of the hydraulic actuating mechanism; I

FIG. 3 is a section similar to FIG. 2 illustrating a further embodiment of the invention wherein the floating piston is mechanically actuated;

FIG. 4 is a section showing a further embodiment wherein the floating piston is actuated by separate hydraulic cylinders and in which the mold parts are in closed position;

FIG. 5 is a section taken on the line 55 of FIG. 4 but showing mold parts in open position;

FIG. 6 is a section similar to FIG. 1 showing the platen as movable vertically and in closed position; and

FIG. 7 is a similar view showing the platen in open position.

Referring to the drawings more in detail, the invention is shown in FIGS. 1 and 2 as embodied in an apparatus mounted on a base 10 which may contain the pumps and sources of hydraulic fluid. The base 10 carries fixed platens 11 and 12 in which carrier rods 13 are mounted. The fixed platen 12 carries a mold part 15. A movable platen 16 carring a mold part 17 is slidably mounted on the rods 13 for movement in a long stroke between molding-and retracted positions. The material that is to be molded in the mold consisting of parts 16 and 17 is supplied to the mold cavity through nozzle 14. I

A hydraulic cylinder 20 is mounted on the fixed platen 11 and extends parallel to the rods 13. This cylinder carries a floating piston 21 and an actuating piston 22. The latter carries a piston rod 23 which extends through the closed end 24 of the cylinder 20 and is attached to the movable platen 16 for actuating the same.

The floating piston 21 is formed with a cylindrical bore 26 in its rearward side into which a pipe 27 extends. The pipe 27 is mounted in the fixed platen II and receives actuating fluid through line 28 and valve 29. The bore 26 constitutes an actuating cylinder which slides over the pipe 27 as the floating piston 21 is advanced or retracted axiallyin the cylinder 20. The piston 21 is locked in advanced position by abutment blocks 30 which extend radially into the cylinder 20 and are actuated by hydraulic cylinders 31 having fluid connections 32 and 33 for advancing or retracting said blocks.

The space 34 in the cylinder 20 between the pistons 21 and 22 constitutes a movable pressure chamber which is supplied with hydraulic fluid by a line 35 and valve 36. The annular space 37 around the piston rod 23 in advance ofthe piston 22 is supplied with hydraulic fluid by a line 38 and through valve 39. The fluid in this latter space acts to retract the piston 22 at the end of the molding cycle.

The fluid in the pressure chamber 34 between the pistons 21 and 22 exerts the holding force to resist the molding pressure. This pressure is supplied by the line 35 which is connected to a suitable source of fluid pressure such as a pump, not shown. If additional holding pressure is required in any particular case a pressure intensifier may be included in the supply line 35.

In the embodiment shown in FIGS. 1 and 2 such a pressure intensifier is shown as formed in the actuating piston 22. This intensifier comprises a bore 40 in the rearward side of the piston 22 communicating through a port 41 with the space 37 and carrying a piston 42 having a rod 43' of smaller diameter extending rearwardly into communication with thefluid in the chamber 34. The arrangement is such that fluid enteringthe bore 40 from the space 37 exerts pressure on the piston 42 and the rod 43 exerts pressure on the fluid in the chamber 34, said pressures having a relationship which is inversely proportional to the difference in cross section areas of the piston 42 and the rod 43.

In operation, at thestart of a molding cycle, fluid pressure is applied to the cylindrical bore 26 through the pipe 27 from the line 28 while the valve 36 is closed to confine the fluid in the chamber 34, while pressure in space 37 is relieved. This fluid pressure causes the floating piston 21 to advance and thereby to advance the fluid within the chamber 34, the actuating piston 22 and the movable platen 16. The stroke continues until the mold parts and 17 are brought into contact. The intensifier piston 42 retracts due to the pressure in chamber 34 that is exerted by floating piston 21.

If this closing stroke is a continuation of the previous molding cycle wherein the clearances have been set, the floating piston 21 will have reached a point beyond the blocks 30 at the end of the closing stroke. The blocks are then advanced into the cylinder by actuation of the cylinders 31 to form an abutment for the floating piston 21 adapted to resist any movement of the parts in response to the molding pressure.

In the event the clearances have not been previously set, at the end of the closing stroke the valve 36 is opened to allow adjustment of the quantity of fluid in the chamber 34 so as to bring the actuating piston 22 into the position corresponding to the height of the open to continue the supply of fluid to the chamber 34.

during the injection of the molding material into the mold cavities, sufflciently to offset the volume compression of the fluid and the leakage that usually takes place from the cylinder 20 through piston rings and gaskets, not shown, that are conventionally provided.

In the event that additional fluid pressure is desired in the chamber 34 for resisting the molding pressure, a pressure intensifier may be used. In the embodiments of FIGS. 1 and 2 this may be accomplished by admitting fluid into the space 37 in advance of the actuating piston 22. The fluid from the space 37 passes through the passage 41 into the bore 40 to exert pressure on the piston head 42 which applies, by means of the rod 43, a correspondingly greater pressure on the fluid in the chamber 34. While the pressure intensifier has been shown as built into the actuating piston, it is obvious that a separate pressure intensifier may be inserted in the line 35 at any convenient point.

At the end of the molding step the valve 36 is released temporarily to relieve the pressure of the floating piston 21 on the abutment blocks 30. These blocks are then retracted by actuation of the cylinders 31, the valve 36 is closed and fluid pressure is introduced into the space 37 in advance of the actuating piston 22 for retracting the pistons and the platen l6 and thus open the mold for the removal of the molded article.

It will be noted that in this molding cycle the quantity of fluid which must be pumped for producing the closing stroke of the pistons is the relatively small quantity required to fill the small diameter of cylinder 26. This is the case in conventional hydraulic presses. In addition, this fluid permits a ready adjustment to be made of the position of the movable platen 16 to accommodate molds of different heights.

FIG. 3 illustrates an embodiment wherein the floating piston is actuated mechanically instead of hydraulically. In this embodiment parts similar to those of FIGS. 1 and 2 i have been given the same reference numbers with the suffix a and will not be redescribed.

In FIG. 3 the floating piston 21a is actuated by a toggle mechanism comprising pivoted links 50 and 51. The link 51 is mounted on a rotatable shaft 52 which may be actuated by a reversible drive such as reversible hydraulic motor which is adapted to be advanced or retracted by the displacement of a small quantity of fluid. The floating piston is advanced and retracted by turning the shaft 52. In order to retract the actuating piston 22a with the floating piston 21a and to maintain the fluid in the chamber 340 under confining pressure a tension spring 53 is disposed between the piston parts in the chamber 34a. Abutment blocks, not shown, similar to blocks 30 of FIG. 2 or other suitable abutment means may be used in this embodiment for resisting the molding pressure.

The floating piston 21a may be retracted by actuation of the shaft 52 in which case the actuating piston 22a may be retracted in part by the action of the tension spring 53 and in part by pressure of fluid introduced into the space 37a from pipe 38a. The rate of introduction of such fluid should be such as to synchronize the retraction of the piston 22a with that of the pistons 21a and thus to retain the confining pressure on the fluid in the chamber 34a. The spring 53 assists in maintaining such synchronization. However, if the relative rates are such that a reduction in pressure occurs in the chamber 34a, additional fluid may be introduced from the space 37a through passage 55 in the actuating piston 22a and check valve 56 which allows fluid to flow into the chamber 340 only. In this way the space is maintained full at all times and any substantial reduction in pressure of the fluid is prevented.

If the toggle mechanism is actuated only on the mold closing stroke the floating piston 211; may be retracted solely by the action of the piston 22a in response to fluid pressure in the space 37a as in FIG. 2, in which case the passage 55 and the spring 53 may be omitted.

Toggle mechanism has been shown in FIG. 3 as an example of mechanical means for actuating the floating piston. It is obvious that other types of mechanical actuating means may be used. The operation of the mechanism of FIG. 3 is otherwise similar to that of FIG. 2. In both cases the molding pressure is resisted by the fluid pressure in the chamber 34 and by the abutments holding the floating piston 21 in place.

The embodiment of FIGS. 4 and 5 is similar to that of FIGS. 1 and 2 except that the pistons are advanced by means of outside cylinders. Parts similar to those of FIGS. 1 and 2 have been given the same reference numbers with the suffix b.

The parts are advanced into closed position by external cylinders 60 having piston rods 61 connected by means of a yoke 62 to the floating piston 21b. Hydraulic fluid is supplied to the cylinders 60 'by lines 63.

The floating piston 21b is formed with an enlarged head 65 which slides in an enlarged bore 66 in the cylinder 20b and engages a shoulder 67 which forms a positioning stop for the piston. The piston may be locked in advanced position by pins 30b actuated by cylinders 31b and adapted to enter an arcuate groove 68in the head 65. Obviously other types of abutment means may be used if desired such as the abutment blocks 30 of FIG. 2.

In operation the floating piston 21b is advanced against the stop shoulder 67 by the cylinders 60 and is locked in position by the pins 30b. The fluid in the chamber 34b is then pressurized to lock the mold parts together as in FIG. 2. If additional holding pressure is required a pressure intensifier may be used as in FIG. 2.

At the end of the molding step the pistonsare retracted by the admission of fluid into the space 37b as previously described.

The embodiment of FIGS. 6 and 7 is generally similar to those above described except that the apparatus is shown as mounted for a vertical stroke and the platens are closed by gravity.

In the embodiment of FIGS. 6 and 7 the floating piston 210 is of greater diameter than the cylinder c and slides in an enlarged bore 70 which terminates in a shoulder 71 which forms a stop to limit the advance of the floating piston 21c. The piston slides through a bore in an abutment ring 72 which is disposed to slide transversely of the cylinder in channels 73 above the top end of the cylinder 20c and is shiftable by an actuating cylinder 74. When so shifted the ring 72 forms an abutment to resist retraction of the piston 21c in response to molding pressure. Since the floating piston 21c is advanced by gravity no other actuating mechanism is shown. However, hydraulic or mechanical actuating mechanism may be used if desired as in the previous forms.

The pistons 21c and 220 and the movable platen 16c are retracted by fluid pressure in the space 37c in advance of the actuating piston 22c in the cylinder 200. This fluid may also serve as a cushioning means for the parts in their closing stroke and may serve as'a safety locking means to lock the parts in elevated position. Additional safety locking means such as a mechanical arm or lever may also be included if desired.

It is to be understood that the various types of actuating means and abutment means shown in the different embodiments are interchangeable and certain forms have been shown for purposes of illustration only. In each of the embodiments the fluid in the pressure chamber 34 between the piston parts 21 and 22, which is confined by the pistons and moves therewith in their closing and retraction strokes, serves when pressurized to provide the force for opposing the molding pressure. The cylinder and the pistons may be made of as large a diameter as required for exerting the desired force without substantially increasing the quantity of hydraulic fluid which must be pumped into or out of the cylinder at each stroke. The fluid remains in the cylinder at all times and only requires pressurizing I during the molding step.

What is claimed is:

1. Molding apparatus comprising a pair of platens adapted to carry mold parts, one of said platens being mounted for movement between an advanced position wherein said mold parts are closed for molding under pressure and a retracted position wherein the mold parts are separated, actuating means for said movable platen comprising a hydraulic cylinder having an actuating piston connected to actuate said movable platen and adapted to be advanced and retracted in said cylinder, a floating piston in said cylinder'spaced from said first piston to form a movable pressure chamber therebetween, adapted to contain a hydraulic fluid suited to exert a pressure on said actuating piston for opposing the molding pressure, means maintaining said hydraulic fluid in said chamber for movement together with said pistons as they advance and retract in said cylinder, and means advancing said floating piston for thereby advancing said fluid and actuating piston into mold closing position, and means locking said floating piston in said advanced position during the molding step.

2. Apparatus as set forth in claim 1 including means maintaining pressure on said fluid to resist retraction movement of said actuating piston.

3. Apparatus as set forth in claim 1 in which hydraulic means is provided for advancing said floating piston.

4. Apparatus as set forth in claim 1 in which mechanical means is provided to advance said floating piston into mold closing position.

5. Apparatus as set forth in claim 1 in which said floating piston is provided with a head projecting beyond said cylinder and in which said external advancing means is connected to actuate said head.

6. Apparatus as set forth in claim 4 in which toggle mechanism is connected to advance said floating piston, said toggle mechanism including a pair of links and a reversible rotatable shaft connected to actuate one of said links.

7. Apparatus as set forth in claim 1 in which said locking means includes abutment elements and means to advance said elements to a position to prevent retraction of said floating piston.

8. Apparatus as set forth in claim 7 in which said elements constitute pins disposed to be advanced into locking position.

9. Apparatus as set forth in claim 7 in which said elements include a slide disposed atthe end of said cylinder and having an opening through which a part of said floating piston passes, and means shifting said slide laterally when said floating piston has advanced 'therebeyond to thereby form a stop to resist retraction of said piston.

10. Apparatus as set forth in claim 1 in which said stop means is provided to limit the advance position of said floating piston.

11. Apparatus as set forth in claim 1 in which pressure intensifier means is provided to increase the fluid pressure in said chamber.

12. Apparatus as set forth in claim 11 in which said pressure intensifier means is carried by said actuating piston.

13. Apparatus as set forth in claim 1 including a space in said cylinder in advance of said actuating piston and means introducing hydraulic fluid into said last space for retracting said pistons from advanced positions. 7

14. Apparatus as set forth in claim 13 in which means is provided for supplying fluid from said last space to said chamber.

15. Apparatus as set forth in claim 13 including means associated with said actuating piston and responsive to fluid pressure in said last space to increase the fluid pressure in said chamber.

confining pressure on saidfluid' in said chamber. 

1. Molding apparatus comprising a pair of platens adapted to carry mold parts, one of said platens being mounted for movement between an advanced position wherein said mold parts are closed for molding under pressure and a retracted position wherein the mold parts are separated, actuating means for said movable platen comprising a hydraulic cylinder having an actuating piston connected to actuate said movable platen and adapted to be advanced and retracted in said cylinder, a floating piston in said cylinder spaced from said first piston to form a movable pressure chamber therebetween, adapted to contain a hydraulic fluid suited to exert a pressure on said actuating piston for opposing the molding pressure, means maintaining said hydraulic fluid in said chamber for movement together with said pistons as they advance and retract in said cylinder, and means advancing said floating piston for thereby advancing said fluid and actuating piston into mold closing position, and means locking said floating piston in said advanced position during the molding step.
 2. Apparatus as set forth in claim 1 including means maintaining pressure on said fluid to resist retraction movement of said actuating piston.
 3. Apparatus as set forth in claim 1 in which hydraulic means is provided for advancing said floating piston.
 4. Apparatus as set forth in claim 1 in which mechanical means is provided to advance said floating piston into mold closing position.
 5. Apparatus as set forth in claim 1 in which said floating piston is provided with a head projecting beyond said cylinder and in which said external advancing means is connected to actuate said head.
 6. Apparatus as set forth in claim 4 in which toggle mechanism is connected to advance said floating piston, said toggle mechanism including a pair of links and a reversible rotatable shaft connected to actuate one of said links.
 7. Apparatus as set forth in claim 1 in which said locking means includes abutment elements and means to advance said elements to a position to prevent retraction of said floating piston.
 8. Apparatus as set forth in claim 7 in which said elements constitute pins disposed to be advanced into locking positioN.
 9. Apparatus as set forth in claim 7 in which said elements include a slide disposed at the end of said cylinder and having an opening through which a part of said floating piston passes, and means shifting said slide laterally when said floating piston has advanced therebeyond to thereby form a stop to resist retraction of said piston.
 10. Apparatus as set forth in claim 1 in which said stop means is provided to limit the advance position of said floating piston.
 11. Apparatus as set forth in claim 1 in which pressure intensifier means is provided to increase the fluid pressure in said chamber.
 12. Apparatus as set forth in claim 11 in which said pressure intensifier means is carried by said actuating piston.
 13. Apparatus as set forth in claim 1 including a space in said cylinder in advance of said actuating piston and means introducing hydraulic fluid into said last space for retracting said pistons from advanced positions.
 14. Apparatus as set forth in claim 13 in which means is provided for supplying fluid from said last space to said chamber.
 15. Apparatus as set forth in claim 13 including means associated with said actuating piston and responsive to fluid pressure in said last space to increase the fluid pressure in said chamber.
 16. Apparatus as set forth in claim 1 in which linking means is disposed between said pistons.
 17. Apparatus as set forth in claim 16 in which said linking means is a tensioning device for maintaining confining pressure on said fluid in said chamber. 